In todays information age, one can find a map
for just about any
occasion. There are countless maps displaying every street in North America,
maps detailing the topography of every patch of land in Europe, maps outlining
the types of forests in Canada, and maps showing all of Indias major
mineral deposits. Maps have even been created that accurately display
everything from ski resorts to scenic drives in North America.

Given the overwhelming number of maps out there, one would expect that
geologists, those whose job it is to understand the Earths make-up, would
have long ago created a complete and accurate global map showing faults,
volcanoes, earthquake epicenters and mountain formations known to have
occurred over the recent geological past of one million years. After all,
these are the phenomena that shape our planets surface
and are responsible for many of our worst natural disasters.

Yet, such a complete map has never been published.
Most global maps of tectonic
activity reflect a somewhat oversimplified view of plate tectonics. They
merely show the jagged outlines of the enormous plates that make up the
crust of
the Earth and the faults at the boundaries of the continents. Few include
active faults that lie in the middle of the plates. A number of the maps
out there are even
based
on older, incomplete research and display ocean rifts and plate boundaries
incorrectly. As a consequence, neither scientists nor students of geology have
had a comprehensive, realistic, view of global tectonic activity.

This cartographic gap may soon be filled. Using modern global databases,
hundreds of research reports, satellite photos, and computerized drafting
methods, a group of researchers at NASA's Goddard Space Flight Center has
pieced together what's considered a series of objective and comprehensive maps
(actually what's known as a Geological Information System, or GIS) of the planet's tectonic activity. The
map shows crustal features such as faults and volcanoes that have been
active within the last one million years. This period was chosen as being
long enough to be truly representative of the Earth's geologic activity,
but short enough that geologic features have not been destroyed by erosion
and can still be recognized. The maps show not only plate boundaries and
large fault zones, but the location of major volcanic eruptions,
earthquake epicenters, and movement of the Earth's crust.

The Goddard team has put all this information on the Internet for educators,
researchers, and students to use. They hope the map will not only provide
working
scientists with an important visualization tool, but will also give future geologists the
information
they need to fill in the gaps of the current theories of global tectonics.

The schematic Global Tectonic Activity Map. It shows
several types of faults, active spreading centers, and volcanoes. The
geologists who prepared it achieved unprecedented completeness by using both
historical data and satellite imagery. (Download full
Digital Tectonic Activity
Maps)

Faulty Fault Zones

Paul Lowman, a geologist at Goddard, came up with
the idea for these maps
twenty-five years ago. He explained he had just started working within the
Geophysics branch at NASA and was searching for a few good maps showing the
plate boundaries and fault zones around the world. "I began digging
through
the literature and all I could find were these schematic plate maps that were
clearly no good at all. They were extremely generalized and often wrong in
places," he said.

Part of the reason for the oversights, he explained, is the theory of plate
tectonics. This is the theory that the Earth's crust (oceanic and
continental) is a mosaic of large rigid plates, more or less floating on
the planet's partly molten rocky mantle. Currents in the mantle constantly
drive these plates, causing them to move apart, by sea-floor spreading, at
mid-ocean ridges, and to collide with one another at their edges. When the
plates collide, or slide past each other, earthquakes and volcanoes occur
and mountains are formed.

"Many of these early plate maps were very subjective and
interpretive as
well," said Lowman. The geologists who put the maps together had
trouble gathering data in remote areas of the world such as in Southeast Asia or the Middle East. Due to this lack of information, those who drew the maps were forced to extrapolate with poorly mapped data. However, space photography soon began to change the
situation.

The majority of earthquakes and
volcanoes around the world occur at the intersection of plate boundaries.
This diagram shows the
subduction of an ocean plate underneath a continental plate. Earthquakes
are caused by the two
plates moving relative to each other, and volcanoes are formed when ocean
crust, forced under
the lighter continental crust, melts and then rises to the Earth's surface.
(Image by Robert Simmon,
NASA GSFC)

Upon seeing
the lack of comprehensive synoptic maps, Lowman decided to make a
tectonic activity map of his own. He had access to images from the NASA
Landsat satellites, as well as 70mm photographs taken by Gemini, Apollo,
and Skylab astronauts. Each Landsat moved in a roughly circular orbit
nearly pole to pole around the Earth, and used multispectral scanners to
gather imaging data of most of the land area of our planet. The data were
sent down in digital form to the surface, so that researchers could make
them into images and examine them. By pouring over these orbital images,
Lowman and other geologists were able to pin down the location of faults
and volcanoes that were not well documented. They drew in many of the
features the other maps missed, and created the foundation for the first
NASA global tectonic activity map, in 1979.

Researchers used Landsat imagery to
pinpoint faults and other geological features. This method ensured that
areas that are not predicted by existing
theories of plate tectonics would be accurately depicted. (Image from Geomorphology from
Space)

Looking for Cracks in the Earth

These early maps that Lowman drew were widely used in
textbooks and scientific journals. However, by 1995, the great expansion
of geologic knowledge and the development of new computerized mapping
techniques called for a new tectonic activity map.

Jacob Yates, another geologist at Goddard, has been involved with the
digital
mapping project from the start. He explained, "We wanted to create a
tectonic activity map a researcher or educator could hold up in their hand
on an
eight and a half by eleven sheet of paper or viewable on their computer screen.

Yates said that they used
the latest global topographic map compiled in digital form by the National
Geophysical Data Center in
Boulder, Colorado. The topographic map depicts ocean ridges, mountain ranges, and the overall terrain of the Earth in a three-dimensional relief.
Yates
explained they also created a second global map that differentiates
between
the Earths oceanic and continental crust. On this map the basaltic
oceanic crust was blocked out in a light blue and the granitic
crust
that makes up our continents was shown in white.

Over the base map, the Goddard team digitized active faults, rifts,
subduction zones, and ocean ridges, which were then digitized. They
included the rates and directions in which the plates were moving away from
the mid-ocean ridges by sea-floor spreading, and showed regions of volcanic
activity in the last one million years.

Detail of the
Goddard
map, showing topography and tectonic features of the East African coast.
The offset red line
in the map excerpt indicates the Indian Ocean Ridge, and its rate of
spread. (View large image or download full
Digital Tectonic Activity Maps)

"The map is really an amalgamation of a lot of research
that we and other
scientists from all over the world have done," Yates explained. To
compile
the information on the map, Lowman and his team combed over dozens of research
papers and older maps prepared by scientists inside and outside of NASA. They
wanted to pin down all the tectonic features over the Earth that are large
enough
to be depicted on a global map.

Satellite photos of the Earth were used to
verify the precise location of faults and volcanoes. In some cases the Goddard
team had to fill in gaps of ground-based research, by utilizing remote-sensing techniques. "Some areas such as Tibet were
simply too
remote. Others like Southeast Asia contained jungles, swamp, yellow fever, and
just bad stuff for geologists," explained Yates. The Goddard team
would use
the satellite images of these hard to reach and dangerous locations to complete
research on faults and other geologic features to ensure they were shown
correctly.

New crust is formed along the mid-ocean ridges.
Plumes of upwelling magma push the plates apart along these ridges at a
rate of 15 cm per year. Underwater volcanoesblack
smokersare a common feature of the ridges. (Image by Robert Simmon,
NASA GSFC)

Detail of the Goddard map, showing topography and tectonic
features of the East African coast. The offset red line in the map excerpt
indicates the Indian Ocean Ridge, and its rate of spread.

As an addendum to the core tectonic
activity map, the Goddard team also made
detailed global maps of earthquakes and active volcanoes  the two hazards
that accompany tectonic activity. The earthquake data were retrieved from the
National Geophysical Data Center and included the epicenters of the more than
200,000 earthquakes with magnitude over 3.5 that occurred between 1963 and
1998. The volcanic data, on
the other hand, were taken from the Smithsonian Global Volcanism Program and
showed the location of roughly 1,200 volcanic eruptions that are known
to have
taken place over the past 10,000 years (Lowman et al., 1999). Older
volcanoes were added from other maps and satellite photos.

The Goddard team integrated all of these data and mapped each
earthquake epicenter and volcanic center on the same base map they
used to
show tectonic activity. Most of the
earthquakes and volcanoes are along or near plate boundaries. However,
many can
be found in unexpected areas. "Rarely do we think of active volcanoes
existing in central China," Yates pointed out.

The final map Lowman and his team pieced together displays the movement
of the
earth's plates. Space geodesy stations all over the globe make precise
measurements of
how far the plates move each year. The movements range
from next
to nothing in Africa to more than 7 centimeters a year in areas such as the
Pacific Basin. The Hawaiian islands, for example, are moving toward Asia
at more than 8 centimeters a year. The Goddard researchers mapped these
stations readings by indicating relative velocity and direction of crustal motion.

Top: Earthquakes
are one of the most destructive natural hazards. The Northridge earthquake
in Southern California killed 57 people
and caused 15 billion dollars of damage. (Photograph courtesy Federal
Emergency Management Agency)

Above: The Goddard geologists mapped earthquakes around the world
from 1963 - 1998. Thousands occurred
in the United States during that time. (Download full
Seismic Activity Map)

A New Tool for Tectonics

"From the start our goal has been to make all
of this information
available to the public," Yates explained. The researchers have held to
this initial objective; they recently posted their maps on their web site (http://denali.gsfc.nasa.gov/dtam/) in a
number of different formats that anyone can download or print. When overlaid on
transparencies, the maps all match up point for point.

Yates said that the maps are likely to provide researchers with a much
needed
reference tool. On these digital maps, geologists can find features not
found on
any other global map of tectonic activity. In the past a scientist would have
had to pore through stacks of research papers to locate the two large active
faults running through the Russian Ural Mountains in the center of the Eurasian
Plate or the dozen or so fractures that scar Tibet and southwestern China.
With
the DTAM, they should now be able to see where these features exist
at a
glance before making a trip to the library.

Regardless of how working scientists use these maps, both Lowman and Yates
believe that the real impact of their research will be on educators and
students.
Already, several textbook manufacturers have shown interest in the maps. "If the maps do become a
standard
in the classroom, were hoping they will contribute to a paradigm shift in
terms of how people view global tectonics," said Yates.

For instance, looking at the digital tectonic activity map, it isnt
hard to notice that the African Plate and the Eurasian Plate are two of the
slowest moving plates in the world, and should be both moving to the east.
The tectonic activity at a plates boundaries should depend on the
plates movement relative to the adjacent plate. Yet, the map also
shows that the
Mediterranean, which forms the boundary between these two plates, has one
of the
highest concentrations of faults, volcanoes and earthquakes in the world in
spite of
the slow movement (Lowman et al., 1999).

By utilizing the DTAM instead of over-simplified "plate maps," educators and students of geology will be
exposed to a synoptic view of global tectonics. The Goddard team hopes that when the students become geologists they may incorporate this knowledge into their
research or even improve on the current theory of plate tectonics.
"Theres a lot more to geology than just plates and we hope down the
road somewhere geologists will start to recognize this," said Lowman.

The Mediterranean Sea is one
of the world's most geologically active areas, even though the regional
plate motion is
relatively slow. (The blue, yellow, and red lines indicate different
types of faults. Red dots
represent volcanoes active within the past million years.) Several other
areas of tectonic activity that are not well explained by
conventional plate tectonics show up on the Digital Tectonic Activity Map.
(View large image, or download full
Digital Tectonic Activity
Maps)

The Mediterranean Sea is one
of the world's most geologically active areas, even though the regional
plate motion is
relatively slow. (The blue, yellow, and red lines indicate different
types of faults. Red dots
represent volcanoes active within the past million years.) Several other
areas of tectonic activity that are not well explained by
conventional plate tectonics show up on the Digital Tectonic Activity Map.